Lattice capacity-dependent activity for CO₂ methanation: crafting Ni/CeO₂ catalysts with outstanding performance at...

In the pursuit of understanding lattice capacity threshold effects of oxide solid solutions for their supported Ni catalysts, a series of Ca²⁺-doped CeO₂ solid solutions with 10 wt% Ni loading (named Ni/CaCe_1-O) was prepared using a sol-gel method and used for CO₂ methanation. The lattice capacity of Ca²⁺ in the lattice of CeO₂ was firstly determined by the XRD extrapolation method, corresponding to a Ca/(Ca + Ce) molar ratio of 11%. When the amount of Ca²⁺ in the CaCe_1-O supports was close to the CeO₂ lattice capacity for Ca²⁺ incorporation, the obtained Ni/Ca_0.1Ce_0.9O catalyst possessed the optimal intrinsic activity for CO₂ methanation. XPS, Raman spectroscopy, EPR and CO₂-TPD analyses revealed the largest amount of highly active moderate-strength alkaline centers generated by oxygen vacancies. The catalytic reaction mechanisms were revealed using in situ IR analysis. The results clearly demonstrated that the structure and reactivity of the Ni/CaCe_1-O catalyst exhibited the lattice capacity threshold effect. The findings offer a new venue for developing highly efficient oxide-supported Ni catalysts for low-temperature CO₂ methanation reaction and enabling efficient catalyst screening.